Improvement of the hierarchical TS-1 properties by silanization of protozeolitic units in presence of alcohols

详细信息    查看全文

• 作者：D.P. Serrano^a ; ^b ; ^{david.serrano@urjc.es} ; ^{david.serrano@imdea.org} ; R. Sanz^a ; P. Pizarro^a ; A. Peral^a ; I. Moreno^a
• 关键词：TS-1 zeolite ; Hierarchical porosity ; Silanization ; Epoxidation
• 刊名：Microporous and Mesoporous Materials
• 出版年：2013
• 出版时间：15 January, 2013
• 年：2013
• 卷：166
• 期：Complete
• 页码：59-66
• 全文大小：1661 K

文摘

The synthesis of hierarchical TS-1 zeolites has been accomplished following a strategy based on the silanization of protozeolitic units. This kind of zeolites is characterized by having a secondary porosity in the supermicro/mesopore range and, therefore, enhanced textural properties. The generation of this secondary porosity is caused by the presence of the silanization agent, which acts as crystal growth inhibitor. However, when a high proportion of organosilane is introduced into the synthesis medium, a highly viscous gel is formed, which reduces the anchoring of the organosilane molecules onto the protozeolitic units. In order to improve the silanization process in these conditions, a variety of alcohols (methanol, ethanol and 2-propanol) has been tested as solvents during the silanization step. The alcohol addition increases the incorporation of the silanization agent onto the zeolite, which is attributed to a reduction in the synthesis media viscosity. Likewise, the alcohols may also undergo grafting onto the external surface of the protozeolitic units through alkoxylation reactions, improving the crystal growth inhibitor effect of the silanization agent. As a consequence, these materials exhibit enhanced textural properties, with a higher secondary porosity contribution, especially when ethanol is used as solvent. Hierarchical TS-1 zeolites prepared adding alcohols in the silanization step show improved catalytic activity in 1-octene epoxidation using tert-butylhydroperoxide as oxidant, due to a higher proportion of more accessible titanium sites. Moreover, it is noteworthy that a reasonable correlation exists between the catalytic activity and the surface attributed to the secondary porosity.